Considering what a memory and resource hog Firefox is, I wouldn't install it even if they were creating it. Note that I'm not endorcing Apple's unfriendly tactics (although to be honest I don't feel an effect from them either) but, should Apple ever allow it, I'd be much more excited to install a version of Chrome with V8 than anything based on Gecko.

2. I believe Chrome as any browser can only use the existing already installed iOS libraries. So there is no v8 on iOS. They all use the same rendering- and javascript-engine. Even worse, HTML5 hybrid-apps aren't even allowed to use the full capabilities as you can with HTML5 in the browser on iOS. Let's just say Apple is pretty strict.

3. There aren't many benchmarks, but the ones I've seen show Firefox on Android is actually faster than Chrome on Android.

4. Firefox on the desktop usually uses less memory than Chrome these days (Chrome memory uses has increased, Firefox has decreased). Depending on addons it is still possible that Firefox will leak memory though, but these problems have become less and less of a problem they fixed most of those problems.

Considering what a memory and resource hog Firefox was, I wouldn't install it even if they were creating it. Note that I'm not endorcing Apple's unfriendly tactics (although to be honest I don't feel an effect from them either) but, should Apple ever allow it, I'd be much more excited to install a version of webkit with V8 than anything based on Gecko because IMHO the javascript engine makes to most difference.